GeneGene
Entire nucleic acid sequence necessary for the Entire nucleic acid sequence necessary for the synthesis of a functional polypeptide (protein chain) synthesis of a functional polypeptide (protein chain)
or functional RNAor functional RNA
Nucleic Acid Sequence
1. DNA (Deoxyribo Nucleic Acid)
2. RNA (Ribo Nucleic Acid)
DNA as Genetic MaterialDNA as Genetic Material
DNA encodes all the information in the cell The composition of the DNA is the same in all cells within an
organism Variation among different cells is achieved by reading the
DNA differently DNA contains four bases that encode all the information to make
an organism’s life
How is Information Encoded in DNA?
How is Information Encoded in DNA?
DNA Consists of four kinds of bases (A,C,G,T) joined to a sugar phosphate backbone
Bases carry the genetic information while the phosphate backbone is structural
Two complementary strands of bases (C-G) and (A-T)
DNA is a Polymer of Deoxyribonucleotide Units
DNA is a Polymer of Deoxyribonucleotide Units
DEOXYRIBONUCLEOTIDE
DEOXY RIBO NUCLEOTIDE
Deoxyribonucleic Acid Deoxyribonucleic Acid (DNA)(DNA)
NucleotideNucleotide:: Phosphate groupPhosphate group 5-carbon sugar5-carbon sugar
Nitrogenous baseNitrogenous base
DNA NucleotideDNA Nucleotide
OO=P-O O
PhosphatePhosphate GroupGroup
NNitrogenous baseNitrogenous base (A, G, C, or T)(A, G, C, or T)
CH2
O
C1C4
C3 C2
5
SugarSugar(deoxyribose)(deoxyribose)
DNA Double HelixDNA Double Helix
NitrogenousNitrogenousBase (A,T,G or C)Base (A,T,G or C)
““Rungs of ladder”Rungs of ladder”
““Legs of ladder”Legs of ladder”
Phosphate &Phosphate &Sugar BackboneSugar Backbone
DNA Double HelixDNA Double Helix
P
P
P
O
O
O
1
23
4
5
5
3
3
5
P
P
PO
O
O
1
2 3
4
5
5
3
5
3
G C
T A
DNA is Composed of Four Different RibonucleotidesDNA is Composed of Four Different Ribonucleotides
HN
CHN
C
CN
CN
C
NH2
HHN
CHN
C
CN
CN
C
O
H2N
H
NC
CC
HN
C
O
CH3
HO
H
NC
CC
N
CH
O
H
H
NH2
Adenine Guanine
Thymine Cytosine
TwoPurines
TwoPyrimidines
9 9
1 1
Nitrogenous BasesNitrogenous Bases
PURINESPURINES
1.1. Adenine (A)Adenine (A)
2.2. Guanine (G)Guanine (G)
PYRIMIDINESPYRIMIDINES
3.3. Thymine (T)Thymine (T)
4.4. Cytosine (C)Cytosine (C)T or C
A or G
BASE-PAIRINGSBASE-PAIRINGS
BaseBase # of # of
PurinesPurines PyrimidinesPyrimidines PairsPairs H-BondsH-Bonds
Adenine (A)Adenine (A) Thymine (T)Thymine (T) A = TA = T 2 2
Guanine (G)Guanine (G) Cytosine (C)Cytosine (C) C GC G 3 3
CG
3 H-bonds
BASE-PAIRINGSBASE-PAIRINGS
CG
H-bonds
T A
Base Pairing Occurs Through Hydrogen Bonds
Base Pairing Occurs Through Hydrogen Bonds
A-TG-C
Chargaff’s RuleChargaff’s Rule
AdenineAdenine must pair with must pair with ThymineThymine
GuanineGuanine must pair with must pair with CytosineCytosine
Their amounts in a given DNA molecule will be Their amounts in a given DNA molecule will be about about the samethe same..
G CT A
Backbone Sugar Molecules
Deoxyribose (DNA) Ribose (RNA)
O
OH
H
OH
H
H
H
HOCH2
HO
OH
OH
H
H
H
HOCH2
HO H
1´
2´3´
4´
5´
1´
2´3´
4´
5´
Ribose= Five Carbon Sugar Molecule
Deoxy ribo nucleotide
The DNA Backbone is a Deoxyribose Polymer
The DNA Backbone is a Deoxyribose Polymer
Deoxyribose sugars are linked by Phosphodiester Bonds
O
P O
O
O-
H2C
O-
O-
OH
OH
H
H
HH
H2C
H2C
HH
H
H
OHH
O
O
P O
O
O
OP
O HH
H
H
OHH
O
HO
5´
3´
5´
5´
3´
3´
2´
2´
2´
1´
1´
1´
5´-p 3´-OH
5´ 3´
5´
3´
5´
3´ 5´
3´O
P O
O
O-
H2C
O-
O-
OH
OH
H
H
HH
H2C
H2C
HH
H
H
OHH
O
O
P O
O
O
OP
O HH
H
H
OHH
O
HO
5´
3´
5´
5´
3´
3´
2´
2´
2´
1´
1´
1´
O
P O
O
O-
H2C
O-
O-
OH
OH
H
H
HH
H2C
H2C
HH
H
H
OHH
O
O
P O
O
O
OP
O HH
H
H
OHH
O
HO
5´
3´
5´
5´
3´
3´
2´
2´
2´
1´
1´
1´
Base
Base
Base
O
P O
O
O-
H2C
O-
O-
OH
OH
H
H
HH
H2C
H2C
HH
H
H
OHH
O
O
P O
O
O
OP
O HH
H
H
OHH
O
HO
5´
3´
5´
5´
3´
3´
2´
2´
2´
1´
1´
1´
NCH
N
NHCN
NH2
O
H
H
HHO
H
H
OCH2PO
O
PO
O
P
O- O-O-
O-
O
(dATP)
Deoxyadenosine 5´-triphosphateO
H
H
HHO
H
H
NCH
N
NHCN
NH2
HOCH2
DeoxyRibonucleotide
DeoxyRibonucleoside Deoxyadenosine
5´
3´ 5´
3´
NC
CC
N
CH
O
H
NH2
NC
CC
HN
C
O
CH3
HO
NC
CC
HN
C
O
CH3
HO
HO
OH
H
H
HHO
P O
O
O
OP
O
OH
H
H
HH
H2C
H2C
HH
H
H
HO
O-
O-
H2C
O-
O
OP
O
T
C
T
A
G
A
=
G C
A T
Double-stranded DNA Forms a Double Helix
Double-stranded DNA Forms a Double Helix
Central Dogma of BiologyCentral Dogma of Biology
DNA, RNA, and the Flow of Information
DNA, RNA, and the Flow of Information
TranslationTranscription
Replication
Central Dogma (Modifications)Central Dogma (Modifications)
Transcription TranslationDNA
(1) Reverse transcription
Replication
RNA
(2)Self Replication
Protein
(3)Self Replication
(2)Ribozymes
RNARNA
A polymer composed of nucleotides that contain A polymer composed of nucleotides that contain the sugar ribose and one of the four bases the sugar ribose and one of the four bases cytosine, adenine, guanine and uracilecytosine, adenine, guanine and uracile
Polynucleotide containing ribose sugar and uracil Polynucleotide containing ribose sugar and uracil instead of thymineinstead of thymine
Genetic material of some virusesGenetic material of some viruses Primary agent for transferring information from Primary agent for transferring information from
the genome to the protein synthetic machinerythe genome to the protein synthetic machinery
RNARNA NUCLEIC ACID, NUCLEIC ACID, SINGLE STRAND,SINGLE STRAND,
PO4, PO4, RIBOSE SUGAR.RIBOSE SUGAR. BASE PAIRS (N):BASE PAIRS (N):
U = URACILU = URACIL A=ADENINEA=ADENINE C=CYTOSINEC=CYTOSINE G=GUANINEG=GUANINE
URACIL(U)
base with a single-ring structure
phosphate group
sugar (ribose)
Types of RNATypes of RNA
Three types ofThree types of RNARNA::
A.A. messenger RNA (mRNA)messenger RNA (mRNA)
B.B. transfer RNA (tRNA)transfer RNA (tRNA)
C.C. ribosome RNA (rRNA)ribosome RNA (rRNA)
Remember: all produced in the Remember: all produced in the nucleusnucleus!!
A. Messenger RNA A. Messenger RNA (mRNA)(mRNA)
Carries the information for a specific Carries the information for a specific proteinprotein..
Made up of 500 to 1000 Made up of 500 to 1000 nucleotides nucleotides long.long.
Made up of Made up of codons codons ((sequence of three bases: AUG - sequence of three bases: AUG - methioninemethionine).).
Each Each codoncodon, is specific for an , is specific for an amino acidamino acid..
A. Messenger RNA A. Messenger RNA (mRNA)(mRNA)
methionine glycine serine isoleucine glycine alanine stopcodon
proteinprotein
A U G G G C U C C A U C G G C G C A U A AmRNAmRNA
startcodon
Primary structure of a proteinPrimary structure of a protein
aa1 aa2 aa3 aa4 aa5 aa6
peptide bonds
codon 2 codon 3 codon 4 codon 5 codon 6 codon 7codon 1
B. Transfer RNA (tRNA)B. Transfer RNA (tRNA)
Made up of 75 to 80 nucleotides long.Made up of 75 to 80 nucleotides long. Picks up the appropriate Picks up the appropriate amino acid amino acid floating in the floating in the
cytoplasm (cytoplasm (amino acid activating enzymeamino acid activating enzyme)) Transports Transports amino acids amino acids to the to the mRNAmRNA.. Have Have anticodonsanticodons that are complementary to that are complementary to mRNAmRNA
codonscodons.. Recognizes the appropriate Recognizes the appropriate codonscodons on the on the mRNAmRNA and and
bonds to them with H-bonds.bonds to them with H-bonds.
codon in mRNA
anticodon
amino acid OH
amino acidattachment site
anticodon
tRNA MOLECULE
amino acid attachment site
The structure of transfer RNA (tRNA)The structure of transfer RNA (tRNA)
B. Transfer RNA (tRNA)B. Transfer RNA (tRNA)
amino acidamino acidattachment siteattachment site
U A C
anticodonanticodon
methionine amino acidamino acid
C. Ribosomal RNA (rRNA)C. Ribosomal RNA (rRNA)
Made up of Made up of rRNArRNA is 100 to 3000 nucleotides long. is 100 to 3000 nucleotides long. Important structural component of a Important structural component of a ribosome.ribosome.
Associates with Associates with proteins proteins to form to form ribosomes.ribosomes.
RibosomesRibosomes
Large and small subunits.Large and small subunits.
Composed of Composed of rRNA (40%) rRNA (40%) and and proteins (60%).proteins (60%).
Both units come together and help bind the Both units come together and help bind the mRNAmRNA and and tRNA.tRNA.
Two sites forTwo sites for tRNAtRNA
a.a. P site P site (first and last (first and last tRNA will attachtRNA will attach))b.b. A site A site
RibosomesRibosomesOriginOrigin CompletComplet
e e ribosomribosomee
RibosomRibosomal al subunitsubunit
rRNA rRNA componentcomponentss
ProteinsProteins
Cytosol Cytosol (eukaryotic (eukaryotic ribosome)ribosome)
80 S80 S 40 S40 S
60 S60 S18 S18 S
5 S5 S
5.8 S5.8 S
25 S25 S
C.30C.30
C.50C.50
ChloroplastChloroplasts s (prokaryotic (prokaryotic ribosome)ribosome)
70 S70 S 30 S30 S
50 S50 S16 S16 S
4.5 S4.5 S
5 S5 S
23 S23 S
C. 24C. 24
C. 35C. 35
MtochondriMtochondrion on (prokaryotic (prokaryotic ribosome)ribosome)
78 S78 S 30 S30 S
50 S50 S18 S18 S
5 S5 S
26 S26 S
C. 33C. 33
C. 35C. 35
RibosomesRibosomes
PSite
ASite
Largesubunit
Small subunit
mRNAmRNA
A U G C U A C U U C G